Banach空间积分双半群的生成条件

研究Banach空间中积分双半群的生成条件.利用算子A的豫解算子,给出了积分双半群T(t)的生成定理.结果表明:如果对任意的x∈X,f∈X*,以及A|λ]<δ,λ∈ρ(A),有∈Lp(R),则存在算子族S(t),t∈R,S(t)强连续且满足积分双半群的定义.     

关于MHR-环的一个问题

ＭＨＲ－环指的是其主右理想适合极小条件的环．本文的环指的是结合环，未必有单位元． Ｆ．Ａ．Ｓｚａｓｚ在他的专著“Ｒａｄｉｃａｌ　ｏｆ　Ｒｉｎｇｓ”［１］中提出一系列问题，其中第３１问题是：是否存在一个诣零ＭＨＲ－环（或任意ＭＨＲ－环），其有限生成右理想不适合极小条件？本文证明了：任意一个ＭＨＲ－环其有限生成右理想均适合极小条件．从而给出了Ｆ．Ａ．Ｓｚａｓｚ第３１问题的完全解答．     

C(t)-I是紧算子的余弦算子函数C(t)

C(t)，t∈R，是Banach空间X中的余弦算子函数，生成元是A，证明了：C(t)-I，A↓t∈R，紧的充要条件是生成元A紧．     

有限生成亚投射模范畴

对一个QF环R,本文证明:其投射左R模范畴是因式分解范畴当且仅当gl.dim R≤1．进一步,若 P(_RR)＝P(R_R)＝0,则其通过左模而得到的亚 Crothendieck群与其通过右模而得到的亚Grothendieck群在同构意义下是一样的．还证明了有限生成亚投射左R－模范畴不仅是一个因式分解范畴而且是一个带积的具有小的骨架子范畴的范畴．     

三分拆的应用——整边三角形

本利用生成函数给出了整边三角形的个数T(n)公式的一个直接证法，然后给出了T（n）的性质，瘼就两种特殊情形给出了T(n)的记数公式。     

弱闭T(N)-模的预零化子的线性等距映象群

本文刻画了弱闭T(N)-模的预零化子的线性等距映象群的无穷小生成元.设U为由N到N的左连续序同态N到N所确定的弱闭T(N)-模,U_⊥为U的预零化子。{Φ_t :t∈R}为U_⊥到U_⊥上的单参数强连续线性等距映象群。若(0)_*=(0),dim(0)+≠1且H_-=H,dim(HH)≥ 2,则存在有界自伴算子K_1,K_2使得{Φ_t :t∈R}的无穷小生成元为α(X)=i(K_1X-XK_2)。     

本原环的Grothendieck群

设R为本原环,对应的忠实既约模为T,且soc(R)≠R,设R=R/soc(R).在文中证明了以下结果: (1)K_o(R)→K_o(R)是满同态,且当soc(R)≠0时,N=Ker(K_o(R)→K_o(R))是由[T]∈K_o(R)生成的循环子群. (2)若soc(R)=0,则存在一个本原环R_1,soc(R_1)≠0,使得R是R_1的同态象,且K_o(R_1)≌K_o(R)⊕N,其中N=Ker(K_o(R_1)→K_o(R))是由[T]∈K_o(R_t)生成的循环子群.     

关于线性算子的右有界拟线性内逆

对于从线性空间到赋范线性空间的线性算子T引入右有界拟线性内逆的概念.在算子值域的闭包R(T)为切比雪夫子空间的条件下,给出右度量内逆的表示.证得:如果算子的值域R(T)非闭且闭包R(T)为切比雪夫的,则必存在不同的右有界拟线性内逆.     

环的左（N，U）－凝聚维数

设R和S是环，U是平坦右R-模，V是平坦右S-模．本中我们证明了(N，(U，V))-lc．dim(R S)=sup((N，U)-lc．dimR，(N，V)-lc．dimS)．     

对称环的扩张

本文首先考虑了对称环的性质和基本的扩张．其次讨论了几种多项式环的对称性,且证明了:如果R是约化环,则R[x]／(xn)是对称环,其中(xn)是由xn生成的理想,n是一个正整数．最后证明了:对一个右Ore环R,R是对称环当且仅当R的古典右商环Q是对称环．     

Convergence rate for predictive recursion estimation of finite mixtures

Predictive recursion (PR) is a fast stochastic algorithm for nonparametric estimation of mixing distributions in mixture models. It is known that the PR estimates of both the mixing and mixture densities are consistent under fairly mild conditions, but currently very little is known about the rate of convergence. Here I first investigate asymptotic convergence properties of the PR estimate under model misspecification in the special case of finite mixtures with known support. Tools from stochastic approximation theory are used to prove that the PR estimates converge, to the best Kullback-Leibler approximation, at a nearly root-n rate. When the support is unknown, PR can be used to construct an objective function which, when optimized, yields an estimate of the support. I apply the known-support results to derive a rate of convergence for this modified PR estimate in the unknown support case, which compares favorably to known optimal rates.     

Strategic revenue management of preemptive versus non-preemptive queues

Consider a two-class unobservable priority queue, with Poisson arrivals, generally distributed service, and strategic customers. Customers are charged a fee when joining the premium class. We analyze the maximum revenue achievable under the non-preemptive (NP) and preemptive-resume (PR) policies, and show that a provider is always better off implementing the PR policy. Further, the maximum revenue under PR is sometimes achieved when only a fraction of the customers join the premium class.     

结合Armijo步长搜索的一类新的记忆梯度算法及其收敛特征

对求解无约束规划的超记忆梯度算法中线搜索方向中的参数,给了一个假设条件,从而确定了它的一个新的取值范围,保证了搜索方向是目标函数的充分下降方向,由此提出了一类新的记忆梯度算法.在去掉迭代点列有界和Armijo步长搜索下,讨论了算法的全局收敛性,且给出了结合形如共轭梯度法FR,PR,HS的记忆梯度法的修正形式.数值实验表明,新算法比Armijo线搜索下的FR、PR、HS共轭梯度法和超记忆梯度法更稳定、更有效.     

Efficient Scheduling Rules in a Combined Make-to-Stock and Make-to-Order Manufacturing System

In this paper, we consider a mixed MTS/MTO policy to manage a single manufacturing facility producing two classes of end-products. A few end-products have high volume demands, whereas a fairly large number of end-products have low volume demands. In this situation, it is appealing to try to produce the high volume products according to an MTS policy and the low volume products according to an MTO policy. The purpose of this paper is to analyze and compare the impact of the choice of the scheduling policy on the overall performance of the system. We consider two policies: the classical FIFO policy and a priority policy (PR). The PR policy gives priority to production orders corresponding to low volume products over production orders corresponding to high volume products. Under some simple stochastic modeling assumptions, we develop analytical/numerical solutions to optimise each system. We then provide insights regarding this issue with the help of numerical examples. It appears that for some range of parameters, the PR rule can outperform the FIFO rule in the sense that, to achieve the same service level constraint, the corresponding cost under the PR rule is much lower. This situation is encountered when the low volume products can be managed with an MTO policy under the PR scheduling rule, while they have to be managed according to an MTS policy under the FIFO scheduling rule. We also derive some theoretical properties that support our empirical findings.     

限制PR共轭梯度法及其全局收敛性

PR共轭梯度法是求解大型无约束优化问题的有效算法之一，但是算法的全局收敛性在理论上一直没有得到解决。本文将PR共轭梯度法中的参数β加以限制，提出了限制R共轭梯度法，证明了Armijo搜索下算法的全局收敛性、数值试验表明算法是很有效的。     

Some Results in the Theory Modulated Filter Banks and Modulated Wavelet Tight Frames

Perfect reconstruction (PR) FIR filter banks, obtained by modulation of a linear-phase, lowpass, prototype filter and of length 2Mm are well known. Recently, PR modulated filter banks (MFBs) with the analysis and synthesis banks obtained from different prototypes have been reported. This paper describes a general form of modulation that includes modulations used in the literature. This modulation depends on an integer parameter, the modulation phase. The PR property is characterized for MFBs with finite and infinite impulse response filters. The MFB PR problem reduces to roughly M/2 two-channel PR problems. A natural dichotomy in the PR conditions leads us to the concepts of Type 1 and Type 2 MFBs. Unitary MFBs are characterized by the M/2 two-channel PR filter banks also being unitary (for FIR filters of length N = 2Mm, these results are given in (Malvar, Electr Lett. 26, June 1990, 906–907; Koilpillai and Vaidyanathan, IEEE Trans. SP40, No. 4, Apr. 1992, 770–783)). We also give a necessary and sufficient condition for a large class (including FIR) unitary MFB prototypes to have symmetric (even or odd) prototype filters, and exhibit unitary MFBs without symmetric prototypes. A parameterization of all FIR unitary MFBs is also given. An efficient design procedure for FIR unitary MFBs is developed. It turns out that MFBs can be implemented efficiently using Type III and Type IV DCTs. Compactly supported modulated wavelet tight frames are shown to exist and completely parameterized. K-regular modulated WTFs are designed numerically and analytically by solving a set of non-linear equations over the parameters. Design of optimal modulated WTFs for the representation of any given signal is described with examples, and this is used to design smooth modulated WTFs.     

Starting-point strategies for an infeasible potential reduction method

We present two strategies for choosing a “hot” starting-point in the context of an infeasible potential reduction (PR) method for convex quadratic programming. The basic idea of both strategies is to select a preliminary point and to suitably scale it in order to obtain a starting point such that its nonnegative entries are sufficiently bounded away from zero, and the ratio between the duality gap and a suitable measure of the infeasibility is small. One of the two strategies is naturally suggested by the convergence theory of the PR method; the other has been devised to reduce the initial values of the duality gap and the infeasibility measure, with the objective of decreasing the number of PR iterations. Numerical experiments show that the second strategy generally performs better than the first, and both outperform a starting-point strategy based on the affine-scaling step.     

分式化时模理论的noforking性质

本文讨论了将分式环Ｓ＾－１Ｒ上的模归约为Ｒ上模时ｎｏｆｏｒｋｉｎｇ性质的保持性，证明了：Ｌｓ＾－１Ｒ中型ｑ是ｐ的ｎｏｆｏｒｋｉｎｇ扩充当且仅当它们在ＬＲ上的限制ｑＲ的一个ｏｆｏｒｋｉｎｇ扩充，还讨论了分式模Ｓ＾－１Ｍ与Ｍ的ｏｆｏｒｋｉｎｇ性质保持的条件。     

Extremal Problems in Some Classes of Holomorphic Functions

Let PRΛ_n be the class of holomorphic functions with positive real part and real Taylor coefficients the first m + 1 of which are common for all these functions. We find: a) The extreme points of the class PRΛ_n. b) The extrema of {f(r): f ∈ PRΛ_n}, {f′(r): f ∈ PRΛ_n} and {f′(r): f ∈ PRΛ_n}. We also solve respective problems for typical real functions.     

On an Approximation to the Mean Response Times of Priority Classes in a Stable G/G/c/PR Queue

Analytic approximations are proposed for the mean response-times of R(≥ 2) priority classes in a stable G/G/c/PR queue with general class interarrival and service time distributions and c(≥ 2) parallel servers under pre-emptive resume (PR) scheduling. The generalized exponential (GE) distributional model is used to represent general distributions with known first two moments per class. The analysis is based on the extension of known heuristic arguments and earlier results regarding the study of the stable GE/GE/c/FCFS (c ≥ 1, single class) and GE/G/1/PR queues. Numerical examples illustrate the accuracy of the proposed approximations in relation to simulations involving different interarrival and service time distributions per class. Moreover, GE-type performance bounds on the system response time per class are defined. Comments on the role of the new mean response time expressions towards the approximation of the joint and marginal queue length distributions of a stable G/G/c/PR queue are included.